1. field of the Invention
This invention relates, in general, to electrical bushings and, more specifically, to cast resin bushings having embedded capacitor sections.
2. Description of the Prior Art
Encapsulating a capacitor structure into a cast epoxy electrical bushing has been accomplished by several prior art arrangements. U.S. Pat. Nos. 3,513,253, 3,769,446 and 3,769,447, which are assigned to the assignee of this invention, teach encapsulating arrangements which are suitable for particular types of capacitor structures and bushing sizes. Briefly, such bushings have been constructed according to the prior art by placing the capacitor structure into a mold along with a suitable conductor stud. An epoxy resin is then injected into the mold and cured. The cylindrical capacitor sections of the capacitor structure are held in place by a suitable arrangement, such as by a fixture located at the ends of the capacitor sections or by special spacers located between the ends of concentric capacitor sections. While these methods are satisfactory for particular bushing types and sizes, certain types of capacitor structures cannot be properly embedded by these prior art techniques.
When the cylindrical capacitor sections are relatively long, the epoxy resin tends to distort the capacitor sections when the epoxy is being injected into the mold. The greatest distortion or displacement usually occurs near the axial center of the capacitor sections due to a lack of radial support in this region. Such displacement is usually greater when a non-porous capacitor section is used, such as one formed from a non-perforated metallic foil.
Therefore, it is desirable, and it is an object of this invention, to provide a bushing and a method of constructing the bushing wherein the center portions of the capacitor sections are not susceptible to distortion when the casting resin is injected into the mold.